Patent literature 1 below discloses a technology of controlling the orientation and zoom of a monitor camera in response to an approach of a transmitter. Specifically, a radio transmitter transmitting an ID code is attached to a person to be monitored. An antenna for detecting an approach of a transmitter is placed in an off-limits area. Once an approach of a transmitter is detected via the antenna, a monitor camera capable of capturing the surroundings of the antenna is automatically selected among a plurality of monitor cameras, and an image taken with the selected camera is displayed on a monitor. In addition, the ID code transmitted from the transmitter is read via the antenna, and based on the height of the person associated in advance with the ID code, the orientation and zoom of the monitor camera are determined.
(Patent Literature 1) Japanese Laid-Open Patent Publication No. 9-46694
Problems to be Solved
In recent years, with proliferation of the Internet, use of a monitoring system has started in which a monitor camera is connected to the Internet to enable transmission of images taken with the monitor camera. Such a system costs low and is easy in placement of a monitor camera, compared with a system using an exclusive line. In even such a system, however, an operator for monitoring images is still necessary. In the future, therefore, a technology permitting not only automatic capturing of a target to be monitored but also automatic retrieval of useful information from images is desired.
Also, with the recent advance of the robot technology, achievement of a home robot for assisting human lives is expected. Such a robot must have the function of detecting the situation surrounding itself and acting in harmony with the surrounding situation. For example, to properly move in a house and work for a person and an object, a robot must detect the position, posture and motion of a person and an object surrounding itself accurately. Otherwise, the robot will not be able to move and work accurately, much less to assist human lives.
With proliferation of portable cameras such as hand-held video cameras, digital cameras and camera-equipped mobile phones, it is increasingly desired that even an unskilled user could photograph a subject properly. For this, it is important to detect the position and the like of a target accurately.
However, the prior art described above finds difficulty in responding to the needs described above. Specifically, the above prior art merely selects a camera capturing a detection target in response to an approach of a transmitter. The prior art falls short of acquiring detailed information such as where the detection target is in a captured image and what posture the target takes. In addition, with use of an antenna to locate the position, a comparatively large error (several meters to high-teen meters) occurs in position information. Therefore, if another person is present near the detection target, it is difficult to distinguish one from the other in an image.
There are conventionally known some technologies of detecting an object from a camera image by only image processing. However, most of these technologies cause frequent occurrence of miss detection in the environment in which humans normally live, although being usable under very restricted conditions, and thus application of these technologies is difficult. Reasons for this are that the dynamic range of a camera itself is limited, that various objects other than the detection target and the background exist, and that the image of one target at the same position may change in various ways with change of sunshine and illumination.
The visual mechanism of the human can detect a target accurately even in an environment having a large change by utilizing an enormous amount of knowledge and rules acquired from experience. Currently, it is greatly difficult to incorporate knowledge and rules as those acquired by the human in equipment. In addition, an enormous processing amount and memory amount will be necessary to achieve such processing, and this will disadvantageously increase the processing time and the cost.
In view of the above problems, an object of the present invention is providing an object detection technology permitting precise detection of the position, posture and the like of a detection target in an image without requiring an enormous processing amount.